EFFICIENT GROUP ID MANAGEMENT FOR WIRELESS LOCAL AREA NETWORKS (WLANs)

ABSTRACT

Certain aspects of the present disclosure provide techniques and apparatus for efficiently managing groups of stations (STAs) receiving simultaneous transmissions in a multiuser multiple-input multiple-output (MU-MIMO) scheme. One example method generally includes; for a first apparatus in a number of groups of apparatuses, allocating a first spatial stream position for each of at least one first group in the number of the groups; and transmitting a first unicast message to the first apparatus, wherein the first unicast message comprises an indication of the allocated spatial stream position for each of the at least one first group and, for each group in the number of the groups, an indication of a membership status, in the group, of the first apparatus.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.13/107,017 (Atty. Dkt. No. 101963), filed May 13, 2011, which claimsbenefit of U.S. Provisional Patent Application Ser. No. 61/345,140(Atty. Dkt. No. 101963P1), filed May 16, 2010, U.S. Provisional PatentApplication Ser. No. 61/366,493 (Atty. Dkt. No. 102450P1), filed Jul.21, 2010, U.S. Provisional Patent Application Ser. No. 61/372,783 (Atty.Dkt. No. 102450P2), filed Aug. 11, 2010, and U.S. Provisional PatentApplication Ser. No. 61/382,859 (Atty. Dkt. No. 102450P3), filed Sep.14, 2010, all of which are herein incorporated by reference.

BACKGROUND

1. Field

Certain aspects of the present disclosure generally relate to wirelesscommunications and, more particularly, to efficiently managing group IDswith overloading for at least some of the groups of stations (STAs)receiving simultaneous downlink transmission in a downlink multiusermultiple-input multiple-output (MU-MIMO) scheme.

2. Background

In order to address the issue of increasing bandwidth requirementsdemanded for wireless communications systems, different schemes arebeing developed to allow multiple user terminals to communicate with asingle access point by sharing the channel resources while achievinghigh data throughputs. Multiple Input Multiple Output (MIMO) technologyrepresents one such approach that has recently emerged as a populartechnique for next generation communication systems. MIMO technology hasbeen adopted in several emerging wireless communications standards suchas the Institute of Electrical and Electronics Engineers (IEEE) 802.11standard. The IEEE 802.11 denotes a set of Wireless Local Area Network(WLAN) air interface standards developed by the IEEE 802.11 committeefor short-range communications (e.g., tens of meters to a few hundredmeters).

A MIMO system employs multiple (N_(T)) transmit antennas and multiple(N_(R)) receive antennas for data transmission. A MIMO channel formed bythe N_(T) transmit and N_(R) receive antennas may be decomposed intoN_(S) independent channels, which are also referred to as spatialchannels, where N_(S)≦min{N_(T), N_(R)}. Each of the N_(S) independentchannels corresponds to a dimension. The MIMO system can provideimproved performance (e.g., higher throughput and/or greaterreliability) if the additional dimensionalities created by the multipletransmit and receive antennas are utilized.

In wireless networks with a single Access Point (AP) and multiple userstations (STAs), concurrent transmissions may occur on multiple channelstoward different stations, both in the uplink and downlink direction.Many challenges are present in such systems.

SUMMARY

Certain aspects of the present disclosure generally apply to a wirelesslocal area network (WLAN) where an access point (AP) has data to send tomultiple stations (STAs). By using the Downlink Spatial DivisionMultiple Access (DL-SDMA) technique, the AP may send data at the sametime towards multiple STAs. Certain aspects of the present disclosuregenerally relate to efficiently managing group IDs with overloading forat least some of the groups of STAs (or other apparatuses) receivingsimultaneous downlink transmission in a downlink multiusermultiple-input multiple-output (MU-MIMO) scheme.

Certain aspects of the present disclosure provide a method for wirelesscommunications. The method generally includes transmitting a messageindicating whether each of a plurality of groups corresponds to only oneor to more than one set of apparatuses, wherein each set of apparatusesis configured to receive simultaneous transmissions; transmittingspatial stream positions for one of the apparatuses, wherein one of thespatial stream positions is associated with each of the groups; andtransmitting at least one of the simultaneous transmission for one ofthe groups based on the spatial stream positions for the one of theapparatuses.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes a transmitterconfigured to transmit a message indicating whether each of a pluralityof groups corresponds to only one or to more than one set ofapparatuses, wherein each set of apparatuses is configured to receivesimultaneous transmissions; transmit spatial stream positions for one ofthe apparatuses, wherein one of the spatial stream positions isassociated with each of the groups; and transmit at least one of thesimultaneous transmissions for one of the groups based on the spatialstream positions for the one of the apparatuses.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes means fortransmitting a message indicating whether each of a plurality of groupscorresponds to only one or to more than one set of apparatuses, whereineach set of apparatuses is configured to receive simultaneoustransmissions; means for transmitting spatial stream positions for oneof the apparatuses, wherein one of the spatial stream positions isassociated with each of the groups; and means for transmitting at leastone of the simultaneous transmissions for one of the groups based on thespatial stream positions for the one of the apparatuses.

Certain aspects of the present disclosure provide a computer-programproduct for wireless communications. The computer-program productgenerally includes a computer-readable medium comprising instructionsexecutable to transmit a message indicating whether each of a pluralityof groups corresponds to only one or to more than one set ofapparatuses, wherein each set of apparatuses is configured to receivesimultaneous transmissions; transmit spatial stream positions for one ofthe apparatuses, wherein one of the spatial stream positions isassociated with each of the groups; and transmit at least one of thesimultaneous transmissions for one of the groups based on the spatialstream positions for the one of the apparatuses.

Certain aspects of the present disclosure provide an access point. Theaccess point generally includes at least one antenna; a transmitterconfigured to transmit, via the at least one antenna, a messageindicating whether each of a plurality of groups corresponds to only oneor to more than one set of apparatuses, wherein each set of apparatusesis configured to receive simultaneous transmissions; transmit, via theat least one antenna, spatial stream positions for one of theapparatuses, wherein one of the spatial stream positions is associatedwith each of the groups; and transmit, via the at least one antenna, atleast one of the simultaneous transmissions for one of the groups basedon the spatial stream positions for the one of the apparatuses.

Certain aspects of the present disclosure provide a method for wirelesscommunications. The method generally includes receiving, at anapparatus, a message indicating whether a group corresponds to only oneor to more than one set of apparatuses, wherein each set of apparatusesis configured to receive simultaneous transmissions; receiving, at theapparatus, a group identifier and a spatial stream position for theapparatus in the group indicated by the group identifier; and using thespatial stream position to parse the received simultaneoustransmissions.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes a receiverconfigured to receive a message indicating whether a group correspondsto only one or to more than one set of apparatuses, wherein each set ofapparatus is configured to receive simultaneous transmissions andwherein the receiver is further configured to receive a group identifierand a spatial stream position for the apparatus in the group indicatedby the group identifier; and a processing system configured to use thespatial stream position to parse the received simultaneoustransmissions.

Certain aspects of the present disclosure provide an apparatus forwireless communications. The apparatus generally includes means forreceiving a message indicating whether a group corresponds to only oneor to more than one set of apparatuses, wherein each set of apparatusesis configured to receive simultaneous transmissions and wherein themeans for receiving is configured to receive a group identifier and aspatial stream position for the apparatus in the group indicated by thegroup identifier; and means for using the spatial stream position toparse the received simultaneous transmissions.

Certain aspects of the present disclosure provide a computer-programproduct for wireless communications. The computer-program productgenerally includes a computer-readable medium comprising instructionsexecutable to receive, at an apparatus, a message indicating whether agroup corresponds to only one or to more than one set of apparatuses,wherein each set of apparatuses is configured to receive simultaneoustransmissions; receive, at the apparatus, a group identifier and aspatial stream position for the apparatus in the group indicated by thegroup identifier; and use the spatial stream position to parse thereceived simultaneous transmissions.

Certain aspects of the present disclosure provide a wireless node. Thewireless node generally includes at least one antenna; a receiverconfigured to receive, at the wireless node via the at least oneantenna, a message indicating whether a group corresponds to only one orto more than one set of wireless nodes, wherein each set of wirelessnodes is configured to receive simultaneous transmissions and whereinthe receiver is further configured to receive a group identifier and aspatial stream position for the wireless node in the group indicated bythe group identifier; and a processing system configured to use thespatial stream position to parse the received simultaneoustransmissions.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above-recited features of the presentdisclosure can be understood in detail, a more particular description,briefly summarized above, may be had by reference to aspects, some ofwhich are illustrated in the appended drawings. It is to be noted,however, that the appended drawings illustrate only certain typicalaspects of this disclosure and are therefore not to be consideredlimiting of its scope, for the description may admit to other equallyeffective aspects.

FIG. 1 illustrates a diagram of a wireless communications network inaccordance with certain aspects of the present disclosure.

FIG. 2 illustrates a block diagram of an example access point and userterminals in accordance with certain aspects of the present disclosure.

FIG. 3 illustrates a block diagram of an example wireless device inaccordance with certain aspects of the present disclosure.

FIG. 4 illustrates an example structure of preamble transmitted from anaccess point in accordance with certain aspects of the presentdisclosure.

FIG. 5 illustrates example operations that may be performed at an accesspoint (AP) to efficiently manage group IDs with overloading for at leastsome of the groups of apparatuses receiving simultaneous transmissions,in accordance with certain aspects of the present disclosure.

FIG. 5A illustrates example means capable of performing the operationsshown in FIG. 5.

FIG. 6 illustrates an example unicast group ID assignment frametransmitted from an access point in accordance with certain aspects ofthe present disclosure.

FIG. 7 illustrates example operations that may be performed at a userterminal to interpret group IDs with overloading for at least some ofthe groups of apparatuses receiving simultaneous transmissions, inaccordance with certain aspects of the present disclosure.

FIG. 7A illustrates example means capable of performing the operationsshown in FIG. 7.

FIG. 8 illustrates example operations that may be performed at an AP toefficiently manage group IDs for groups of apparatuses receivingsimultaneous transmissions, in accordance with certain aspects of thepresent disclosure.

FIG. 8A illustrates example means for performing the operations shown inFIG. 8.

FIG. 9 illustrates an example unicast group ID assignment frametransmitted from an AP for fully overloaded and partially overloadedgroups, in accordance with certain aspects of the present disclosure.

FIG. 10 illustrates example operations that may be performed at an AP toefficiently manage groups of apparatuses receiving simultaneouslytransmitted spatial streams using default spatial stream positions for aportion of the groups, in accordance with certain aspects of the presentdisclosure.

FIG. 10A illustrates example means for performing the operations shownin FIG. 10.

FIG. 11 illustrates example contents of a unicast message transmittedfrom an AP to a particular user terminal with a default spatial streamposition for the user terminal in each of 32 groups, in accordance withcertain aspects of the present disclosure.

FIG. 12 illustrates example operations that may be performed at a userterminal to parse received simultaneously transmitted spatial streamsusing default spatial stream positions for a portion of a group ofapparatuses, in accordance with certain aspects of the presentdisclosure.

FIG. 12A illustrates example means for performing the operations shownin FIG. 12.

FIG. 13 illustrates example operations that may be performed at an AP toefficiently manage groups of apparatuses receiving simultaneouslytransmitted spatial streams, based on amounts of traffic the apparatusesare expected to receive, in accordance with certain aspects of thepresent disclosure.

FIG. 13A illustrates example means for performing the operations shownin FIG. 13.

FIG. 14 illustrates example contents of a unicast message transmittedfrom an AP to a particular user terminal with a spatial stream positionfor the user terminal in each power savings group, in accordance withcertain aspects of the present disclosure.

FIG. 15 illustrates example operations that may be performed at an AP toefficiently manage groups of apparatuses receiving simultaneouslytransmitted spatial streams using, for at least one of the apparatuses,a membership status and a spatial stream position for each of thegroups, in accordance with certain aspects of the present disclosure.

FIG. 15A illustrates example means capable of performing the operationsshown in FIG. 15.

FIG. 16 illustrates an example unicast group ID assignment frametransmitted from an AP to a particular user terminal with a membershipstatus and a spatial stream position for each group, in accordance withcertain aspects of the present disclosure.

FIG. 17 illustrates example operations that may be performed at a userterminal to parse received simultaneously transmitted spatial streamsusing spatial stream positions for a group of apparatuses, in accordancewith certain aspects of the present disclosure.

FIG. 17A illustrates example means capable of performing the operationsshown in FIG. 17.

DETAILED DESCRIPTION

Various aspects of the disclosure are described more fully hereinafterwith reference to the accompanying drawings. This disclosure may,however, be embodied in many different forms and should not be construedas limited to any specific structure or function presented throughoutthis disclosure. Rather, these aspects are provided so that thisdisclosure will be thorough and complete, and will fully convey thescope of the disclosure to those skilled in the art. Based on theteachings herein one skilled in the art should appreciate that the scopeof the disclosure is intended to cover any aspect of the disclosuredisclosed herein, whether implemented independently of or combined withany other aspect of the disclosure. For example, an apparatus may beimplemented or a method may be practiced using any number of the aspectsset forth herein. In addition, the scope of the disclosure is intendedto cover such an apparatus or method which is practiced using otherstructure, functionality, or structure and functionality in addition toor other than the various aspects of the disclosure set forth herein. Itshould be understood that any aspect of the disclosure disclosed hereinmay be embodied by one or more elements of a claim.

The word “exemplary” is used herein to mean “serving as an example,instance, or illustration.” Any aspect described herein as “exemplary”is not necessarily to be construed as preferred or advantageous overother aspects.

Although particular aspects are described herein, many variations andpermutations of these aspects fall within the scope of the disclosure.Although some benefits and advantages of the preferred aspects arementioned, the scope of the disclosure is not intended to be limited toparticular benefits, uses, or objectives. Rather, aspects of thedisclosure are intended to be broadly applicable to different wirelesstechnologies, system configurations, networks, and transmissionprotocols, some of which are illustrated by way of example in thefigures and in the following description of the preferred aspects. Thedetailed description and drawings are merely illustrative of thedisclosure rather than limiting, the scope of the disclosure beingdefined by the appended claims and equivalents thereof.

An Example Wireless Communication System

The techniques described herein may be used for various broadbandwireless communication systems, including communication systems that arebased on an orthogonal multiplexing scheme. Examples of suchcommunication systems include Spatial Division Multiple Access (SDMA),Time Division Multiple Access (TDMA), Orthogonal Frequency DivisionMultiple Access (OFDMA) systems, Single-Carrier Frequency DivisionMultiple Access (SC-FDMA) systems, and so forth. An SDMA system mayutilize sufficiently different directions to simultaneously transmitdata belonging to multiple user terminals. A TDMA system may allowmultiple user terminals to share the same frequency channel by dividingthe transmission signal into different time slots, each time slot beingassigned to different user terminal. An OFDMA system utilizes orthogonalfrequency division multiplexing (OFDM), which is a modulation techniquethat partitions the overall system bandwidth into multiple orthogonalsub-carriers. These sub-carriers may also be called tones, bins, etc.With OFDM, each sub-carrier may be independently modulated with data. AnSC-FDMA system may utilize interleaved FDMA (IFDMA) to transmit onsub-carriers that are distributed across the system bandwidth, localizedFDMA (LFDMA) to transmit on a block of adjacent sub-carriers, orenhanced FDMA (EFDMA) to transmit on multiple blocks of adjacentsub-carriers. In general, modulation symbols are sent in the frequencydomain with OFDM and in the time domain with SC-FDMA.

The teachings herein may be incorporated into (e.g., implemented withinor performed by) a variety of wired or wireless apparatuses (e.g.,nodes). In some aspects, a wireless node implemented in accordance withthe teachings herein may comprise an access point or an access terminal.

An access point (“AP”) may comprise, be implemented as, or known asNodeB, Radio Network Controller (“RNC”), eNodeB, Base Station Controller(“BSC”), Base Transceiver Station (“BTS”), Base Station (“BS”),Transceiver Function (“TF”), Radio Router, Radio Transceiver, BasicService Set (“BSS”), Extended Service Set (“ESS”), Radio Base Station(“RBS”), or some other terminology.

An access terminal (“AT”) may comprise, be implemented as, or known asan access terminal, a subscriber station, a subscriber unit, a mobilestation, a remote station, a remote terminal, a user terminal, a useragent, a user device, user equipment, a user station, or some otherterminology. In some implementations, an access terminal may comprise acellular telephone, a cordless telephone, a Session Initiation Protocol(“SIP”) phone, a wireless local loop (“WLL”) station, a personal digitalassistant (“PDA”), a handheld device having wireless connectioncapability, a Station (“STA”), or some other suitable processing deviceconnected to a wireless modem. Accordingly, one or more aspects taughtherein may be incorporated into a phone (e.g., a cellular phone or smartphone), a computer (e.g., a laptop), a portable communication device, aportable computing device (e.g., a personal data assistant), anentertainment device (e.g., a music or video device, or a satelliteradio), a global positioning system device, or any other suitable devicethat is configured to communicate via a wireless or wired medium. Insome aspects, the node is a wireless node. Such wireless node mayprovide, for example, connectivity for or to a network (e.g., a widearea network such as the Internet or a cellular network) via a wired orwireless communication link.

FIG. 1 illustrates a multiple-access multiple-input multiple-output(MIMO) system 100 with access points and user terminals. For simplicity,only one access point 110 is shown in FIG. 1. An access point isgenerally a fixed station that communicates with the user terminals andmay also be referred to as a base station or some other terminology. Auser terminal may be fixed or mobile and may also be referred to as amobile station, a wireless device or some other terminology. Accesspoint 110 may communicate with one or more user terminals 120 at anygiven moment on the downlink and uplink. The downlink (i.e., forwardlink) is the communication link from the access point to the userterminals, and the uplink (i.e., reverse link) is the communication linkfrom the user terminals to the access point. A user terminal may alsocommunicate peer-to-peer with another user terminal A system controller130 couples to and provides coordination and control for the accesspoints.

While portions of the following disclosure will describe user terminals120 capable of communicating via Spatial Division Multiple Access(SDMA), for certain aspects, the user terminals 120 may also includesome user terminals that do not support SDMA. Thus, for such aspects, anAP 110 may be configured to communicate with both SDMA and non-SDMA userterminals. This approach may conveniently allow older versions of userterminals (“legacy” stations) to remain deployed in an enterprise,extending their useful lifetime, while allowing newer SDMA userterminals to be introduced as deemed appropriate.

The system 100 employs multiple transmit and multiple receive antennasfor data transmission on the downlink and uplink. The access point 110is equipped with N_(ap) antennas and represents the multiple-input (MI)for downlink transmissions and the multiple-output (MO) for uplinktransmissions. A set of K selected user terminals 120 collectivelyrepresents the multiple-output for downlink transmissions and themultiple-input for uplink transmissions. For pure SDMA, it is desired tohave N_(ap)≧K≧1 if the data symbol streams for the K user terminals arenot multiplexed in code, frequency or time by some means. K may begreater than N_(ap) if the data symbol streams can be multiplexed usingTDMA technique, different code channels with CDMA, disjoint sets ofsubbands with OFDM, and so on. Each selected user terminal transmitsuser-specific data to and/or receives user-specific data from the accesspoint. In general, each selected user terminal may be equipped with oneor multiple antennas (i.e., N_(ut)≧1). The K selected user terminals canhave the same or different number of antennas.

The MIMO system 100 may be a time division duplex (TDD) system or afrequency division duplex (FDD) system. For a TDD system, the downlinkand uplink share the same frequency band. For an FDD system, thedownlink and uplink use different frequency bands. The MIMO system 100may also utilize a single carrier or multiple carriers for transmission.Each user terminal may be equipped with a single antenna (e.g., in orderto keep costs down) or multiple antennas (e.g., where the additionalcost can be supported). The system 100 may also be a TDMA system if theuser terminals 120 share the same frequency channel by dividingtransmission/reception into different time slots, each time slot beingassigned to different user terminal 120.

FIG. 2 illustrates a block diagram of access point 110 and two userterminals 120 m and 120 x in the MIMO system 100. The access point 110is equipped with N_(t) antennas 224 a through 224 t. User terminal 120 mis equipped with N_(ut,m) antennas 252 ma through 252 mu, and userterminal 120 x is equipped with N_(ut,x) antennas 252 xa through 252 xu.The access point 110 is a transmitting entity for the downlink and areceiving entity for the uplink. Each user terminal 120 is atransmitting entity for the uplink and a receiving entity for thedownlink. As used herein, a “transmitting entity” is an independentlyoperated apparatus or device capable of transmitting data via a wirelesschannel, and a “receiving entity” is an independently operated apparatusor device capable of receiving data via a wireless channel. In thefollowing description, the subscript “dn” denotes the downlink, thesubscript “up” denotes the uplink, N_(up) user terminals are selectedfor simultaneous transmission on the uplink, N_(dn) user terminals areselected for simultaneous transmission on the downlink, N_(up) may ormay not be equal to N_(dn), and N_(up) and N_(dn) may be static valuesor can change for each scheduling interval. The beam-steering or someother spatial processing technique may be used at the access point anduser terminal.

On the uplink, at each user terminal 120 selected for uplinktransmission, a TX data processor 288 receives traffic data from a datasource 286 and control data from a controller 280. TX data processor 288processes (e.g., encodes, interleaves, and modulates) the traffic datafor the user terminal based on the coding and modulation schemesassociated with the rate selected for the user terminal and provides adata symbol stream. A TX spatial processor 290 performs spatialprocessing on the data symbol stream and provides N_(ut,m) transmitsymbol streams for the N_(ut,m) antennas. Each transmitter unit (TMTR)254 receives and processes (e.g., converts to analog, amplifies,filters, and frequency upconverts) a respective transmit symbol streamto generate an uplink signal. N_(ut,m) transmitter units 254 provideN_(ut,m) uplink signals for transmission from N_(ut,m) antennas 252 tothe access point.

N_(up) user terminals may be scheduled for simultaneous transmission onthe uplink. Each of these user terminals performs spatial processing onits data symbol stream and transmits its set of transmit symbol streamson the uplink to the access point.

At access point 110, N_(ap) antennas 224 a through 224 ap receive theuplink signals from all N_(up) user terminals transmitting on theuplink. Each antenna 224 provides a received signal to a respectivereceiver unit (RCVR) 222. Each receiver unit 222 performs processingcomplementary to that performed by transmitter unit 254 and provides areceived symbol stream. An RX spatial processor 240 performs receiverspatial processing on the N_(ap) received symbol streams from N_(ap)receiver units 222 and provides N_(up) recovered uplink data symbolstreams. The receiver spatial processing is performed in accordance withthe channel correlation matrix inversion (CCMI), minimum mean squareerror (MMSE), soft interference cancellation (SIC), or some othertechnique. Each recovered uplink data symbol stream is an estimate of adata symbol stream transmitted by a respective user terminal. An RX dataprocessor 242 processes (e.g., demodulates, deinterleaves, and decodes)each recovered uplink data symbol stream in accordance with the rateused for that stream to obtain decoded data. The decoded data for eachuser terminal may be provided to a data sink 244 for storage and/or acontroller 230 for further processing.

On the downlink, at access point 110, a TX data processor 210 receivestraffic data from a data source 208 for N_(dn) user terminals scheduledfor downlink transmission, control data from a controller 230, andpossibly other data from a scheduler 234. The various types of data maybe sent on different transport channels. TX data processor 210 processes(e.g., encodes, interleaves, and modulates) the traffic data for eachuser terminal based on the rate selected for that user terminal TX dataprocessor 210 provides N_(dn) downlink data symbol streams for theN_(dn) user terminals. A TX spatial processor 220 performs spatialprocessing (such as a precoding or beamforming, as described in thepresent disclosure) on the N_(dn) downlink data symbol streams, andprovides N_(ap) transmit symbol streams for the N_(ap) antennas. Eachtransmitter unit 222 receives and processes a respective transmit symbolstream to generate a downlink signal. N_(ap) transmitter units 222providing N_(ap) downlink signals for transmission from N_(ap) antennas224 to the user terminals.

At each user terminal 120, N_(ut,m) antennas 252 receive the N_(ap)downlink signals from access point 110. Each receiver unit 254 processesa received signal from an associated antenna 252 and provides a receivedsymbol stream. An RX spatial processor 260 performs receiver spatialprocessing on N_(ut,m) received symbol streams from N_(ut,m) receiverunits 254 and provides a recovered downlink data symbol stream for theuser terminal. The receiver spatial processing is performed inaccordance with the CCMI, MMSE or some other technique. An RX dataprocessor 270 processes (e.g., demodulates, deinterleaves and decodes)the recovered downlink data symbol stream to obtain decoded data for theuser terminal.

At each user terminal 120, a channel estimator 278 estimates thedownlink channel response and provides downlink channel estimates, whichmay include channel gain estimates, SNR estimates, noise variance and soon. Similarly, a channel estimator 228 estimates the uplink channelresponse and provides uplink channel estimates. Controller 280 for eachuser terminal typically derives the spatial filter matrix for the userterminal based on the downlink channel response matrix H_(dn,m) for thatuser terminal Controller 230 derives the spatial filter matrix for theaccess point based on the effective uplink channel response matrixH_(up,eff). Controller 280 for each user terminal may send feedbackinformation (e.g., the downlink and/or uplink eigenvectors, eigenvalues,SNR estimates, and so on) to the access point. Controllers 230 and 280also control the operation of various processing units at access point110 and user terminal 120, respectively.

FIG. 3 illustrates various components that may be utilized in a wirelessdevice 302 that may be employed within a wireless communication system,such as the MIMO system 100. The wireless device 302 is an example of adevice that may be configured to implement the various methods describedherein. The wireless device 302 may be an access point 110 or a userterminal 120.

The wireless device 302 may include a processor 304 which controlsoperation of the wireless device 302. The processor 304 may also bereferred to as a central processing unit (CPU). Memory 306, which mayinclude both read-only memory (ROM) and random access memory (RAM),provides instructions and data to the processor 304. A portion of thememory 306 may also include non-volatile random access memory (NVRAM).The processor 304 typically performs logical and arithmetic operationsbased on program instructions stored within the memory 306. Theinstructions in the memory 306 may be executable to implement themethods described herein.

The wireless device 302 may also include a housing 308 that may includea transmitter 310 and a receiver 312 to allow transmission and receptionof data between the wireless device 302 and a remote location. Thetransmitter 310 and receiver 312 may be combined into a transceiver 314.A single or a plurality of transmit antennas 316 may be attached to thehousing 308 and electrically coupled to the transceiver 314. Thewireless device 302 may also include (not shown) multiple transmitters,multiple receivers, and multiple transceivers.

The wireless device 302 may also include a signal detector 318 that maybe used in an effort to detect and quantify the level of signalsreceived by the transceiver 314. The signal detector 318 may detect suchsignals as total energy, energy per subcarrier per symbol, powerspectral density and other signals. The wireless device 302 may alsoinclude a digital signal processor (DSP) 320 for use in processingsignals.

The various components of the wireless device 302 may be coupledtogether by a bus system 322, which may include a power bus, a controlsignal bus, and a status signal bus in addition to a data bus.

In next generation WLANs, such as the MIMO system 100 from FIG. 1,downlink (DL) multi-user (MU) MIMO transmission may represent apromising technique to increase overall network throughput. In mostaspects of a DL MU-MIMO transmission, a non-beamformed portion of apreamble transmitted from an access point to a plurality of userstations (STAs) may carry a spatial stream allocation field indicatingallocation of spatial streams to the STAs.

In order to parse this allocation information at a STA side, each STAmay need to know its ordering or a STA number in a set of STAs from theplurality of STAs scheduled to receive the MU transmission. This mayentail forming groups, wherein a group identification (ID) field in thepreamble may convey, to the STAs, the set of STAs (and their order)being transmitted in a given MU transmission. With preamble bits addingto the transmission overhead, it may be desirable to expend as littlebits on the group ID (sometimes written as “groupID” or “group_ID”) aspossible, while not sacrificing on the flexibility with which STAs canbe scheduled together in a MU-MIMO transmission at a given instant.

Preamble Structure with Group Definition

FIG. 4 illustrates an example structure of a preamble 400 in accordancewith certain aspects of the present disclosure. The preamble 400 may betransmitted, for example, from the access point (AP) 110 to the userterminals 120 in the MIMO system 100 illustrated in FIG. 1.

The preamble 400 may comprise an omni-legacy portion 402 (i.e., thenon-beamformed portion) and a precoded IEEE 802.11ac VHT (Very HighThroughput) portion 404. The legacy portion 402 may comprise: a LegacyShort Training Field (L-STF) 406, a Legacy Long Training Field 408, aLegacy Signal (L-SIG) field 410, and two OFDM symbols for VHT Signal A(VHT-SIG-A) fields 412, 414. The VHT-SIG-A fields 412, 414 (i.e.,VHT-SIG-A1 and VHT-SIG-A2) may be transmitted omni-directionally and mayindicate allocation of numbers of spatial streams to a combination (set)of STAs.

The precoded IEEE 802.11ac VHT portion 404 may comprise a VHT ShortTraining Field (VHT-STF) 418, a VHT Long Training Field 1 (VHT-LTF1)420, VHT Long Training Fields (VHT-LTFs) 422, a VHT Signal B (VHT-SIG-B)field 424, and a data portion 426. The VHT-SIG-B field may comprise oneOFDM symbol and may be transmitted precoded/beamformed.

Robust MU-MIMO reception may involve the AP transmitting all VHT-LTFs422 to all supported STAs. The VHT-LTFs 422 may allow each STA toestimate a MIMO channel from all AP antennas to the STA's antennas. TheSTA may utilize the estimated channel to perform effective interferencenulling from MU-MIMO streams corresponding to other STAs. To performrobust interference cancellation, each STA may be expected to know whichspatial stream belongs to that STA, and which spatial streams belong toother users.

As aforementioned, a group ID field 416 may be included in the preamble400 for certain aspects to convey to all supported STAs that aparticular set of STAs will be receiving spatial streams of a MU-MIMOtransmission. For other aspects, the group ID may be indicated as partof another field in the preamble 400, such as within the VHT-SIG-Afields 412, 414 (e.g., bits 4-9 in VHT-SIG-A1). As a baseline, if groupsare formed which may be mapped to unique sets of STAs, a very largenumber of group ID bits within the preamble 400 may be involved forcomplete scheduling flexibility. On the other hand, if overloading of agroup ID is allowed where multiple sets (combinations) of STAs may bemapped to one group ID, greater flexibility may be achieved in thenumber of STAs that can be scheduled together.

Example Efficient Group ID Management for WLANs

As described above, groups may be formed in DL MU-MIMO transmission forWLANs for conveying the spatial stream positions to STAs.Overloading—which generally refers to mapping one group ID to multipleSTA combinations, as used herein—for some or all of the groups allowsflexibility at the AP to trade off between support for more STAcombinations and power saving. Ideally, a group ID management schemeshould be flexible enough to support both overloaded and non-overloadedgroups, as well as support APs with only non-overloaded groups.Accordingly, what is needed is a group ID management scheme thatachieves the above objectives for overloading with a low overhead.

FIG. 5 illustrates example operations 500 that may be performed at an APto efficiently manage group IDs with overloading for at least some ofthe groups of apparatuses receiving simultaneous transmissions, such assimultaneous downlink transmissions in a DL MU-MIMO scheme. Theoperations 500 may begin, at 502, by transmitting a message indicatingwhether each of a plurality of groups corresponds to only one set or tomore than one set of apparatuses, wherein each set of apparatuses isconfigured to receive simultaneous transmissions. For certain aspects,the transmitted message may be a broadcast message or may be one ofmultiple messages transmitted to apparatuses (e.g., STAs) in a BSS. At504, the AP may transmit spatial stream positions for one of theapparatuses, one of the spatial stream positions for each of the groups.For certain aspects, the AP may generate and transmit a frame for one ofthe plurality of apparatuses, wherein the frame may include the groupidentifier (e.g., a field containing a group identification, or groupID) and the spatial stream position for the one of the plurality ofapparatuses in each of the plurality of groups. At 506, the AP maytransmit at least one of the simultaneous transmissions for one of thegroups based on the spatial stream positions for the one of theapparatuses. For certain aspects, the AP may transmit a group identifierindicating the one of the groups during association with the apparatusor to indicate a change to the overloading in the one of the groups.

For certain aspects, the message transmitted at 502 may comprise abeacon frame, a type of management frame in IEEE 802.11-based wirelesslocal area networks (WLANs). Typically containing all the informationabout the network, beacon frames may be broadcasted periodically by theAP to announce the presence of the WLAN. The beacon frame may comprise abitmap conveying the overloading status of the Basic Service Set (BSS),wherein the BSS refers to the AP together with all associated STAs. Inother words, the bitmap may convey which groups are overloaded and whichare non-overloaded, with one bit for each group, for example. Forcertain aspects, the bitmap value may equal 1 for overloaded groups and0 for non-overloaded groups, or vice versa for other aspects. In thebitmap, bits for groups that are never used may be set to 0.

The group ID field may comprise y bits. Therefore, the bitmap maycontain 2^(y) bits to have one bit for every group. For example, thegroup ID field may have 6 bits, and the bitmap may comprise 64 bits.

For certain aspects, the frame generated and transmitted at 504 maycomprise a unicast group ID assignment frame 600 as illustrated in FIG.6. For certain aspects, the unicast group ID assignment frame 600 may betransmitted during association with a STA, such as a STA entering orre-entering a WLAN. The group ID assignment frame 600 may comprise apreamble 400, a media access control (MAC) header 602, a frame body 604,and a frame check sequence (FCS) 606. The frame body 604 may comprise acategory field 608 indicating VHT and an action field 610 indicatingthat the information following the action field 610 is for a group IDassignment as depicted in FIG. 6.

The frame body 604 of the group ID assignment frame 600 may alsocomprise two sections: Section A 612 and Section B 614. Section A mayindicate STA positions in non-overloaded groups (i.e., groupscorresponding to only one set of STAs). Section A may be sent only toSTAs who are members of a non-overloaded group. Section A may compriseup to n different bundles of group information 616, one set of groupinformation for each of the non-overloaded groups. The group information616 may comprise a group ID value 618 and a STA position 620 for the STAdesignated to receive the unicast group ID assignment frame 600. Forcertain aspects, the group ID value 618 may comprise 6 bits (the same asthe group ID field 416), and the STA position 620 may comprise 2 bitsrepresenting four different positions within each group, leading to atotal of 8 bits (i.e., 1 byte) for each bundle of group information 616.

Section B may indicate STA positions 622 for every group, not just thenon-overloaded groups. Thus, if the group ID field 416 comprises y bits,Section B may include 2^(y) STA positions 622. Section B may be includedin the unicast group ID assignment frame 600 whenever a group in the BSSis overloaded. Upon reception of the frame 600, a STA may use the STApositions allocated during association in Section B. For certainaspects, the STA positions 622 may each comprise 2 bits representingfour different STA positions within each group. As an example, if y=6such that there are 64 (=2⁶) groups, Section B may comprise 128 bits (16bytes).

The unicast group ID assignment frame 600 may also contain a field 624indicating the number of non-overloaded group fields in Section A and afield 626 indicating the number of overloaded group fields in Section B.The values in fields 624 and 626 may most likely add up to the totalnumber of groups being used by the AP.

In situations where a BSS has only non-overloaded groups, Section B 614may be absent from the unicast group ID assignment frame 600. In suchsituations, the overloading bitmap in the beacon frame may contain allzeros.

Other than during association with a STA, the unicast group IDassignment frame 600 described above may also be transmitted when agroup changes from being overloaded to being non-overloaded. In thiscase, Section A 612 may be transmitted to STAs who are members of thenew non-overloaded group, without Section B 614 being included in thegroup ID assignment frame 600. Furthermore, the AP may turn off the bit(i.e., change the bit value from 1 to 0) for that new non-overloadedgroup in the overloading bitmap of the beacon frame or other (broadcast)message.

In contrast, when a group changes from being non-overloaded to beingoverloaded, just the message (e.g., the beacon frame) may be sufficientto indicate the change. In other words, the unicast group ID assignmentframe 600 need not be sent in this case. The AP may turn on the bit(i.e., change the bit value from 0 to 1) in the (broadcast) messagecorresponding to the new overloaded group and transmit the message.

FIG. 7 illustrates example operations 700 that may be performed at auser terminal to interpret group IDs with overloading for at least someof the groups of apparatuses receiving simultaneous transmissions suchas simultaneous downlink transmissions in a DL MU-MIMO scheme. Theoperations 700 may begin, at 702, by receiving, at an apparatus (e.g., aSTA), a message indicating whether a group corresponds to only one or tomore than one set of apparatuses, wherein each set of apparatuses isconfigured to receive simultaneous transmissions. For certain aspects,the received message may be a broadcast message or may be one ofmultiple messages transmitted to the apparatus. At 704, the apparatusmay receive a group identifier and a spatial stream position for theapparatus in the group indicated by the group identifier. For certainaspects, the apparatus may receive a frame comprising the groupidentifier (e.g., a group ID field) indicating the group and the spatialstream position for the apparatus. At 706, the apparatus may use thespatial stream position to parse the received simultaneoustransmissions. For certain aspects, the frame may comprise multiplespatial stream positions, one spatial stream position for the apparatusin each of the plurality of groups.

In this manner, overloading for some of the groups may be accomplishedand may allow flexibility at the AP to trade off between support formore STA combinations and power saving. As disclosed herein, the groupID management scheme may be flexible enough to support APs with bothoverloaded and non-overloaded groups and APs with only non-overloadedgroups. This scheme also achieves these benefits for overloading with alow overhead.

Example Group ID Management with Fully and Partially Overloaded Groups

As described above, a STA position in a group may be a number between 1and 4 for a limit of 4 users per MU-MIMO transmission. The STA positionmay be used to parse the Nsts field. A fully overloaded group, asdefined herein, generally refers to a group of STAs where every STA inthe BSS has a STA position for the group. In fully overloaded groups,STAs cannot stop decoding the preamble 400 after decoding the VHT-SIG-Afields 412, 414. In contrast, a partially overloaded group, as definedherein, generally refers to a group of STAs where less than all the STAs(i.e., a subset of the STAs) in the BSS are assigned STA positions forthe group. STAs which are not assigned spatial stream positions can stopdecoding the preamble 400 after decoding the VHT-SIG-A fields 412, 414.Designating partially overloaded groups in this manner provides forpower savings.

FIG. 8 illustrates example operations 800 that may be performed at an APto efficiently manage group IDs for groups of apparatuses. The groups ofapparatuses may receive simultaneous transmissions, such as simultaneousdownlink transmissions in a DL MU-MIMO scheme.

The operations 800 may begin, at 802, by defining one or more groups ofapparatuses, wherein each of the apparatuses is associated with at leastone of the groups. The groups of apparatuses may be in a Basic ServiceSet (BSS). At 804, the AP may assign to each of the apparatuses aspatial stream position for each of the associated groups.

At 806, the AP may transmit a unicast message to one of the apparatuses,wherein the unicast message comprises an indication of the assignedspatial stream position for each of the associated groups. For certainaspects, the one or more groups may comprise at least one fullyoverloaded group comprising all the apparatuses in the BSS. For certainaspects, the one or more groups may further comprise one or morepartially overloaded groups comprising less than all the apparatuses inthe BSS, wherein the one of the apparatuses belongs to at least one ofthe partially overloaded groups

The AP may transmit the simultaneously transmitted spatial streams forone of the groups of the apparatuses, based on the assigned spatialstream position for each of the apparatuses associated with the group.

FIG. 9 illustrates an example unicast group ID assignment frame 900transmitted from an AP for fully overloaded and partially overloadedgroups, in accordance with certain aspects of the present disclosure.The assignment frame 900 may be similar to the assignment frame 600described above with respect to FIG. 6. The frame body 604 of theunicast group ID assignment frame 900 may comprise two sections: SectionA 902 and Section B 904.

Section A 902 may indicate STA positions in partially overloaded groups(i.e., groups corresponding to a subset of all the STAs in the BSS).Section A may be sent only to STAs who are members of a partiallyoverloaded group. Section A may comprise up to n different bundles ofgroup information 910, one set of group information for each of thepartially overloaded groups. The group information 910 may comprise agroup ID value 912 and a STA position 914 for the STA designated toreceive the unicast group ID assignment frame 900. For certain aspects,the group ID value 912 may comprise 6 bits (the same as the group IDfield 416), and the STA position 914 may comprise 2 bits representingfour different positions within each group, leading to a total of 8 bits(i.e., 1 byte) for each bundle of group information 910.

For certain aspects, Section B 904 may indicate STA positions 906 forevery group, not just the partially overloaded groups. Thus, if thegroup ID field 416 comprises y bits, Section B may include 2^(y) STApositions 906. For other aspects Section B may indicate STA positions906 for only the fully overloaded groups. Upon reception of the frame900, a STA may use the STA positions allocated during association inSection B 904. For certain aspects, the STA positions 906 may eachcomprise 2 bits representing four different STA positions within eachgroup. As an example, if y=6 such that there are 64 (=2⁶) groups,Section B 904 may comprise 128 bits (16 bytes).

The unicast group ID assignment frame 900 may also contain a field 916indicating the number of partially overloaded group fields (i.e., thenumber of bundles of group information 910) in Section A and a field 908indicating the number of overloaded group fields in Section B. Thevalues in these fields 908, 916 may, in certain aspects, add up to thetotal number of groups being used by the AP.

In situations where a BSS has only fully overloaded groups, Section A902 may be absent from the unicast group ID assignment frame 900.

The unicast group ID assignment frame 900 may be transmitted duringassociation of a STA with the AP in the BSS. By transmitting the frame900 during association, the group ID assignment frame 900 may convey atleast the STA positions 906 in fully overloaded groups and may alsoconvey the STA positions 914 if the STA is a member of any partiallyoverloaded groups. The unicast group ID assignment frame 900 may also betransmitted when a group changes from fully overloaded to partiallyoverloaded. In this latter case, Section A 902 may be transmitted onlyto STAs who are members of the new partially overloaded group.

Each MU-MIMO transmission may carry an overloading status bit in theVHT-SIG-A fields 412, 414. This overloading status bit may equal 1 ifthe group ID is being used in a fully overloaded transmission and 0 fora partially overloaded transmission. The AP may use the overloadingstatus bit to indicate that a group has moved from partially overloadedto fully overloaded. In other words, the AP may turn OFF the overloadingstatus bit while simultaneously transmitting the spatial streams using agroup ID for a partially overloaded group. Whenever this partiallyoverloaded group changes to a fully overloaded group, the AP indicatesthis by turning ON the overloading status bit while simultaneouslytransmitting the spatial streams using that group ID. Changing from apartially overloaded to a fully overloaded group can occur when one ormore STAs who were not members of a partially overloaded group leave theBSS, such that all of the STAs remaining in the BSS belong to the group.

Overloading for some of the groups may provide flexibility at the AP totrade off between support for increased STA combinations and powersavings. Group ID management may be flexible enough to support APs withfully overloaded and partially-overloaded groups and APs with onlynon-overloaded groups. The group ID management solutions described aboveachieve these objectives with a low messaging overhead.

Example Group ID Management Schemes

As described above, the group ID field 416 has many uses. Certainaspects of the present disclosure also provide various group IDmanagement processes. For certain aspects, support for nearly all STAcombinations (e.g., a 6-bit group ID) may be enabled through a one-timemessage at association, providing low messaging overhead. Furthermore,an optional power savings may be enabled at the STAs through unicast(and hence, robust) messaging to a small subset of STAs.

Allocation of Default Spatial Stream Positions

FIG. 10 illustrates example operations 1000 that may be performed at anAP to efficiently manage groups of apparatuses using default spatialstream positions for a portion of the groups. The groups of apparatusesmay receive simultaneously transmitted spatial streams, such assimultaneous downlink transmissions in a DL MU-MIMO scheme.

The operations 1000 may begin, at 1002, by determining a portion of anumber of groups of apparatuses. The number of the groups of apparatusesmay be determined based on the number of bits in a group ID. Forexample, a 6-bit group ID may have 64 groups of apparatuses. The portionof the number of groups may be a subset of the number of groups. Forexample, the portion may comprise 32 groups out of 64 possible groups.

For a first one of the apparatuses at 1004, a default spatial streamposition may be allocated for each group in the portion of the groups.This allocation may occur during association of a the first one of theapparatuses (e.g., a user terminal).

At 1006, a first unicast message may be transmitted to the first one ofthe apparatuses, wherein the first unicast message comprises anindication of the allocated default spatial stream position for eachgroup in the portion of the groups. This unicast message may betransmitted during association of the first one of the apparatuses.

At association, every user terminal (or STA) may be allocated a defaultspatial stream position for a subset of the number of groups (e.g., 32groups out of 64). For example, FIG. 11 illustrates example contents1100 of a unicast message transmitted from an AP to a particular userterminal with a default spatial stream position for the user terminal ineach of 32 groups. The subset of the number of groups that will beassigned default spatial stream positions may be determined by the AP.The contents 1100 are conceptually illustrated with rows of groupnumbers 1102 and columns of STA spatial stream positions 1104. Symbol xat row i, column j means that the STA is allocated position j for groupnumber i. As described above, two bits may be used to indicate STAposition (1, 2, 3 or 4) per group in the unicast message, and six bits,for example, may be used to indicate the group number (i.e., group ID).

Default spatial stream positions allocated during association may beconsidered as pre-provisions for supporting a large number of STAswithout further messaging. For example, 96% of the STA combinations in aBSS with 100 STAs may be supported if default positions for 32 groupsare allocated for each STA.

Allocating default spatial stream positions during association may alsoavoid the disadvantage of designing for the current network size, andthen expanding later. In other words, this solution avoids having tosend additional messages to the existing members every time a new STA isadmitted to the BSS, thereby increasing group ID management efficiency.

For example, consider a BSS with 10 STAs and assume all the ¹⁰C₄ (10choose 4, or the number of STA combinations having a size of 4 spatialstream positions in 10 STAs) STA combinations are supported with thecurrent group assignments. When an eleventh STA joins the BSS, anadditional ¹⁰C₃=120 STA combinations may most likely need to besupported. A scheme which expands with network size would likely requiremessages to each of the existing 10 members as well as the new STA. Eachexisting STA would most likely need to be sent information for ⁹C₂ newSTA combinations.

Aspects of the present disclosure with pre-provisioned default spatialstream positions, however, need not transmit any messages to theexisting members of the BSS to update the STA combinations. Rather, onlya single unicast message may be sent to the eleventh STA, typicallyduring association, to inform the eleventh STA of which groups this newSTA is a member.

FIG. 12 illustrates example operations 1200 to parse receivedsimultaneously transmitted spatial streams using default spatial streampositions for a portion of a group of apparatuses. The operations 1200may be performed by a user terminal, for example.

The operations 1200 may begin, at 1202, by receiving a unicast messagecomprising an indication of a default spatial stream position for eachgroup in a portion of a number of groups of apparatuses. At 1204,simultaneously transmitted spatial streams for one of the groups of theapparatuses may be received, wherein the unicast message and thesimultaneously transmitted spatial streams are received at one of theapparatuses. At 1206, the default spatial stream position for the one ofthe groups may be used to parse the received simultaneously transmittedspatial streams.

Power Savings for STAs

As another or additional group ID management scheme, there may be apower savings scheme for the user terminals. Opportunities for powersavings may arise under many conditions, such as when a small subset ofthe user terminals is receiving most of the traffic in a large network.The association time messaging described above may not be enough toprovide power savings because every user terminal has to listen to alltransmissions.

To solve this problem, FIG. 13 illustrates example operations 1300 toefficiently manage groups of apparatuses receiving simultaneouslytransmitted spatial streams, based on amounts of traffic being sent tothe apparatuses. The operations 1300 may be performed at an AP, forexample.

For certain aspects, the operations 1300 may begin, at 1302, bydetermining one or more first apparatuses being expected to receive(i.e., being sent) substantially more traffic than one or more secondapparatuses. For example, the one or more first apparatuses may be beingsent most of the traffic. This determination may be made based on athreshold amount of traffic, wherein the one or more first apparatusesare being expected to receive more than the threshold amount.

At 1304, one or more groups of the first apparatuses may be defined,wherein each of the first apparatuses is associated with at least one ofthe groups. These groups may be considered as power-save groups. At1306, each of the first apparatuses may be assigned a spatial streamposition for each of the associated groups. A first message may betransmitted at 1308 to one of the first apparatuses, wherein the firstmessage comprises an indication of the assigned spatial stream positionin each of the associated groups for the one of the first apparatuses.The first message may comprise a unicast message or a multicast message.For certain aspects, multiple unicast messages may be transmitted, oneunicast message to each of the first apparatuses, while in otheraspects, one multicast message may be transmitted to all, or at leastsome, of the first apparatuses.

A unicast message may be transmitted to each of the relevant userterminals with the assigned spatial stream position in each of thepower-save groups for a particular one of the relevant user terminals.For example, FIG. 14 illustrates example contents 1400 of a unicastmessage transmitted from an AP to a particular user terminal (or STA)with a spatial stream position for the user terminal in each of threepower-save groups. The contents 1400 are conceptually illustrated withrows of power-save group numbers 1402 and columns of STA spatial streampositions 1104. Symbol x at row i, column j means that the STA isallocated position j for power-save group number i. As described above,two bits may be used to indicate STA position (1, 2, 3, or 4) perpower-save group in the unicast message, and six bits, for example, maybe used to indicate the power-save group number (i.e., power-save groupID).

For certain aspects, the power-save groups may be formed of relevantuser terminals (e.g., those receiving most of the traffic) using groupIDs which are not used for the default spatial stream positionsdescribed above. For example, with a 6-bit group ID, there may be 64different groups. If the first 32 groups (having group IDs ranging from0 to 31) are used for default spatial stream positions, then any one ormore of the remaining 32 groups (having group IDs ranging from 32 to 63)may be used to define any power-save groups. In the example of FIG. 14,the first 32 groups are used for default spatial stream positions, andtherefore, group IDs 35, 50, and 63 may be used for the power savegroups.

As an example power savings operation, consider a BSS with 100 STAs andassume that 5 of the STAs are receiving most of the traffic. In thiscase, ⁵C₄ power-save groups may be formed to support the 5 STAs. Unicastmessages may be transmitted only to each of the 5 STAs, wherein eachunicast message comprises the power-save groups relevant to a particularSTA intended to receive the message. Messages are not sent to theremaining 95 STAs informing these STAs of the power-save groups. Forcertain aspects, even though 5 STAs are receiving most of the traffic,less than the 5 STAs may be associated with one or more power-savegroups.

During subsequent MU-MIMO transmissions to a power-save group, only theSTAs that are members of the particular power-save group listen to thetransmissions. The remaining 95 STAs ignore the transmissions, as doones of the 5 STAs who are not members of the particular power-savegroup.

Once a power-save group has been created, this group may be purged in aneffort to free up a group ID. To purge a power-save group, the AP maysend a unicast message to relevant user terminals (i.e., user terminalswho were associated with the particular power-save group), informingthem that a power-save group is being dissolved. This purging processmay handle scenarios where this group of user terminals are no longerbeing sent enough traffic (e.g., not substantially more traffic thanother user terminals outside the power-save group). Once a power-savegroup has been purged, the group ID may be freed up for newassociations.

Unicast Group ID Assignment

A group ID assignment should most likely be acknowledged before thatparticular group ID can be used. Currently, there is no acknowledgmentscheme available for broadcast messages. Furthermore, managing multiuser(MU) group membership on a per-STA basis generally seems like a cleanerdesign. For example, most events in the network will happenindependently across STAs.

FIG. 15 illustrates example operations 1500 that may be performed at anAP to efficiently manage groups of apparatuses using, for at least oneof the apparatuses, a membership status and a spatial stream positionfor each of the groups. The groups of apparatuses may receivesimultaneously transmitted spatial streams, such as simultaneousdownlink transmissions in a DL MU-MIMO scheme.

The operations 1500 may begin, at 1502, by allocating, for a firstapparatus in a number of groups of apparatuses, a first spatial streamposition for each of at least one first group in the number of thegroups. This allocation may occur during association of the first one ofthe apparatuses (e.g., a user terminal).

At 1504, a first unicast message may be transmitted to the firstapparatus, wherein the first unicast message comprises an indication ofthe allocated spatial stream position for each of the at least one firstgroup and, for each group in the number of the groups, an indication ofa membership status, in the group, of the first apparatus. This unicastmessage may be transmitted during association of the first one of theapparatuses.

FIG. 16 illustrates an example unicast group ID assignment frame 1600transmitted from an AP to a particular user terminal. This unicastmessage may be transmitted during association with the user terminal orany time the group assignment of the user terminal is updated. The framebody 604 may comprise a group ID table 1601, wherein the group ID tablecomprises a number of group ID fields 1602 for group ID management. Eachgroup ID field 1602 may be associated with a certain group, and thegroup ID fields 1602 may be ordered in the frame body 604 according tothe group number (e.g., the group ID).

Each group ID field 1602 may indicate a membership status 1604 for theparticular user terminal in the group associated with the field 1602.The membership status 1604 may comprise a single bit. For certainaspects, a value of “1” for the membership status 1604 in a given groupID field 1602 may indicate that the particular user terminal is a memberof the group associated with the given group ID field 1602, whereas avalue of “0” may indicate that the particular user terminal is not amember of this group. Each group ID field 1602 may also comprise anindication of a spatial stream position (e.g., a STA position 1606). Asdescribed above, two bits may be used to indicate the STA position (00,01, 10, or 11) per group ID field 1602 in the unicast group IDassignment frame 1600.

For certain aspects, the group ID assignment frame 1600 may comprise afield 1608 indicating a number y of group ID bits. The number of groupID bits indicated by the field 1608 may provide the particular userterminal receiving the frame 1600 with the number of fields 1602 in thegroup ID table 1601. For example, if y group ID bits are indicated bythe field 1608, then the group ID assignment frame 1600 may include2^(y) group ID fields.

Thus, this field 1608 provides flexibility, such that the group IDassignment frame 1600 need not include group ID fields 1602 for allpossible groups according to the group ID field 416. For example, an APfor a small network may use shorter unicast group ID assignment messageswhen the AP operates with less than 64 groups. This scenario may beappropriate in a home environment, where just a few groups may besufficient. Furthermore, the flexibility offered by including the field1608 may provide for any future increases in the size of the group ID(i.e., greater than 6 bits).

For certain aspects, the unicast group ID assignment frame 1600 may beencrypted before transmission. Such encryption may prevent rogue groupID assignments.

FIG. 17 illustrates example operations 1700 to parse receivedsimultaneously transmitted spatial streams using spatial streampositions for a group of apparatuses. The operations 1700 may beperformed by a user terminal, for example.

The operations 1700 may begin, at 1702, by receiving a unicast messagecomprising, for each group in a number of groups, an indication of amembership status in the group and an indication of a spatial streamposition. At 1704, simultaneously transmitted spatial streams for one ofthe groups of the apparatuses may be received, wherein the unicastmessage and the simultaneously transmitted spatial streams are receivedat one of the apparatuses (e.g., at the user terminal). At 1706, the oneof the apparatuses may be determined to be a member of the one of thegroups based on the indication of the membership status. At 1708, theindication of the spatial stream position for the one of the groups maybe used to parse the received simultaneously transmitted spatialstreams.

The various operations of methods described above may be performed byany suitable means capable of performing the corresponding functions.The means may include various hardware and/or software component(s)and/or module(s), including, but not limited to a circuit, anapplication specific integrated circuit (ASIC), or processor. Generally,where there are operations illustrated in figures, those operations mayhave corresponding counterpart means-plus-function components withsimilar numbering. For example, operations 500 illustrated in FIG. 5correspond to means 500A illustrated in FIG. 5A.

For example, means for transmitting may comprise a transmitter (e.g.,the transmitter unit 222) and/or an antenna 224 of the access point 110illustrated in FIG. 2. Means for receiving may comprise a receiver(e.g., the receiver unit 254) and/or an antenna 252 of the user terminal120 illustrated in FIG. 2. Means for processing, means for determining,or means for using may comprise a processing system, which may includeone or more processors, such as the RX data processor 270, the TX dataprocessor 288, and/or the controller 280 of the user terminal 120illustrated in FIG. 2.

As used herein, the term “determining” encompasses a wide variety ofactions. For example, “determining” may include calculating, computing,processing, deriving, investigating, looking up (e.g., looking up in atable, a database or another data structure), ascertaining, and thelike. Also, “determining” may include receiving (e.g., receivinginformation), accessing (e.g., accessing data in a memory), and thelike. Also, “determining” may include resolving, selecting, choosing,establishing, and the like.

As used herein, a phrase referring to “at least one of” a list of itemsrefers to any combination of those items, including single members. Asan example, “at least one of: a, b, or c” is intended to cover: a, b, c,a-b, a-c, b-c, and a-b-c.

The various illustrative logical blocks, modules and circuits describedin connection with the present disclosure may be implemented orperformed with a general purpose processor, a digital signal processor(DSP), an application specific integrated circuit (ASIC), a fieldprogrammable gate array (FPGA) or other programmable logic device (PLD),discrete gate or transistor logic, discrete hardware components, or anycombination thereof designed to perform the functions described herein.A general-purpose processor may be a microprocessor, but in thealternative, the processor may be any commercially available processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

The steps of a method or algorithm described in connection with thepresent disclosure may be embodied directly in hardware, in a softwaremodule executed by a processor, or in a combination of the two. Asoftware module may reside in any form of storage medium that is knownin the art. Some examples of storage media that may be used includerandom access memory (RAM), read only memory (ROM), flash memory, EPROMmemory, EEPROM memory, registers, a hard disk, a removable disk, aCD-ROM, and so forth. A software module may comprise a singleinstruction, or many instructions, and may be distributed over severaldifferent code segments, among different programs, and across multiplestorage media. A storage medium may be coupled to a processor such thatthe processor can read information from, and write information to, thestorage medium. In the alternative, the storage medium may be integralto the processor.

The methods disclosed herein comprise one or more steps or actions forachieving the described method. The method steps and/or actions may beinterchanged with one another without departing from the scope of theclaims. In other words, unless a specific order of steps or actions isspecified, the order and/or use of specific steps and/or actions may bemodified without departing from the scope of the claims.

The functions described may be implemented in hardware, software,firmware, or any combination thereof. If implemented in hardware, anexample hardware configuration may comprise a processing system in awireless node. The processing system may be implemented with a busarchitecture. The bus may include any number of interconnecting busesand bridges depending on the specific application of the processingsystem and the overall design constraints. The bus may link togethervarious circuits including a processor, machine-readable media, and abus interface. The bus interface may be used to connect a networkadapter, among other things, to the processing system via the bus. Thenetwork adapter may be used to implement the signal processing functionsof the PHY layer. In the case of a user terminal 120 (see FIG. 1), auser interface (e.g., keypad, display, mouse, joystick, etc.) may alsobe connected to the bus. The bus may also link various other circuitssuch as timing sources, peripherals, voltage regulators, powermanagement circuits, and the like, which are well known in the art, andtherefore, will not be described any further.

The processor may be responsible for managing the bus and generalprocessing, including the execution of software stored on themachine-readable media. The processor may be implemented with one ormore general-purpose and/or special-purpose processors. Examples includemicroprocessors, microcontrollers, DSP processors, and other circuitrythat can execute software. Software shall be construed broadly to meaninstructions, data, or any combination thereof, whether referred to assoftware, firmware, middleware, microcode, hardware descriptionlanguage, or otherwise. Machine-readable media may include, by way ofexample, RAM (Random Access Memory), flash memory, ROM (Read OnlyMemory), PROM (Programmable Read-Only Memory), EPROM (ErasableProgrammable Read-Only Memory), EEPROM (Electrically ErasableProgrammable Read-Only Memory), registers, magnetic disks, opticaldisks, hard drives, or any other suitable storage medium, or anycombination thereof. The machine-readable media may be embodied in acomputer-program product. The computer-program product may comprisepackaging materials.

In a hardware implementation, the machine-readable media may be part ofthe processing system separate from the processor. However, as thoseskilled in the art will readily appreciate, the machine-readable media,or any portion thereof, may be external to the processing system. By wayof example, the machine-readable media may include a transmission line,a carrier wave modulated by data, and/or a computer product separatefrom the wireless node, all which may be accessed by the processorthrough the bus interface. Alternatively, or in addition, themachine-readable media, or any portion thereof, may be integrated intothe processor, such as the case may be with cache and/or generalregister files.

The processing system may be configured as a general-purpose processingsystem with one or more microprocessors providing the processorfunctionality and external memory providing at least a portion of themachine-readable media, all linked together with other supportingcircuitry through an external bus architecture. Alternatively, theprocessing system may be implemented with an ASIC (Application SpecificIntegrated Circuit) with the processor, the bus interface, the userinterface in the case of an access terminal), supporting circuitry, andat least a portion of the machine-readable media integrated into asingle chip, or with one or more FPGAs (Field Programmable Gate Arrays),PLDs (Programmable Logic Devices), controllers, state machines, gatedlogic, discrete hardware components, or any other suitable circuitry, orany combination of circuits that can perform the various functionalitydescribed throughout this disclosure. Those skilled in the art willrecognize how best to implement the described functionality for theprocessing system depending on the particular application and theoverall design constraints imposed on the overall system.

The machine-readable media may comprise a number of software modules.The software modules include instructions that, when executed by theprocessor, cause the processing system to perform various functions. Thesoftware modules may include a transmission module and a receivingmodule. Each software module may reside in a single storage device or bedistributed across multiple storage devices. By way of example, asoftware module may be loaded into RAM from a hard drive when atriggering event occurs. During execution of the software module, theprocessor may load some of the instructions into cache to increaseaccess speed. One or more cache lines may then be loaded into a generalregister file for execution by the processor. When referring to thefunctionality of a software module below, it will be understood thatsuch functionality is implemented by the processor when executinginstructions from that software module.

If implemented in software, the functions may be stored or transmittedover as one or more instructions or code on a computer-readable medium.Computer-readable media include both computer storage media andcommunication media including any medium that facilitates transfer of acomputer program from one place to another. A storage medium may be anyavailable medium that can be accessed by a computer. By way of example,and not limitation, such computer-readable media can comprise RAM, ROM,EEPROM, CD-ROM or other optical disk storage, magnetic disk storage orother magnetic storage devices, or any other medium that can be used tocarry or store desired program code in the form of instructions or datastructures and that can be accessed by a computer. Also, any connectionis properly termed a computer-readable medium. For example, if thesoftware is transmitted from a website, server, or other remote sourceusing a coaxial cable, fiber optic cable, twisted pair, digitalsubscriber line (DSL), or wireless technologies such as infrared (IR),radio, and microwave, then the coaxial cable, fiber optic cable, twistedpair, DSL, or wireless technologies such as infrared, radio, andmicrowave are included in the definition of medium. Disk and disc, asused herein, include compact disc (CD), laser disc, optical disc,digital versatile disc (DVD), floppy disk, and Blu-ray® disc where disksusually reproduce data magnetically, while discs reproduce dataoptically with lasers. Thus, in some aspects computer-readable media maycomprise non-transitory computer-readable media (e.g., tangible media).In addition, for other aspects computer-readable media may comprisetransitory computer-readable media (e.g., a signal). Combinations of theabove should also be included within the scope of computer-readablemedia.

Thus, certain aspects may comprise a computer program product forperforming the operations presented herein. For example, such a computerprogram product may comprise a computer-readable medium havinginstructions stored (and/or encoded) thereon, the instructions beingexecutable by one or more processors to perform the operations describedherein. For certain aspects, the computer program product may includepackaging material.

Further, it should be appreciated that modules and/or other appropriatemeans for performing the methods and techniques described herein can bedownloaded and/or otherwise obtained by a user terminal and/or basestation as applicable. For example, such a device can be coupled to aserver to facilitate the transfer of means for performing the methodsdescribed herein. Alternatively, various methods described herein can beprovided via storage means (e.g., RAM, ROM, a physical storage mediumsuch as a compact disc (CD) or floppy disk, etc.), such that a userterminal and/or base station can obtain the various methods uponcoupling or providing the storage means to the device. Moreover, anyother suitable technique for providing the methods and techniquesdescribed herein to a device can be utilized.

It is to be understood that the claims are not limited to the preciseconfiguration and components illustrated above. Various modifications,changes and variations may be made in the arrangement, operation anddetails of the methods and apparatus described above without departingfrom the scope of the claims.

1. A method for wireless communications, comprising: in a number ofgroups of apparatuses, determining one or more first groups to which afirst apparatus belongs; allocating, for the first apparatus, a firstspatial stream position associated with each of the one or more firstgroups; generating a first message based on the allocation and thedetermination; and transmitting the first message to the firstapparatus, wherein the first message comprises: an indication of theallocated first spatial stream position associated with each of the oneor more first groups; and an indication of whether the first apparatusis a member of each group in the number of groups.
 2. The method ofclaim 1, wherein transmitting the first message comprises transmittingthe first message during association with the first apparatus.
 3. Themethod of claim 1, wherein the first message comprises a fieldindicating a number of group identification (groupID) bits and whereinthe number of groups of apparatuses is based on the number of thegroupID bits.
 4. The method of claim 3, wherein the field indicates thatthe number of groupID bits is y such that the number of groups ofapparatuses is 2^(y).
 5. The method of claim 1, wherein the indicationof whether the first apparatus is a member of each group comprises onebit for each group in the number of groups.
 6. The method of claim 1,wherein the indication of the allocated first spatial stream positionassociated with each of the one or more first groups comprises two bits.7. The method of claim 1, further comprising: in the number of groups,determining one or more second groups to which a second apparatusbelongs; allocating, for the second apparatus, a second spatial streamposition associated with each of the one or more second groups;generating a second message based on the allocation and thedetermination; and transmitting the second message to the secondapparatus, wherein the second message comprises: an indication of theallocated second spatial stream position associated with each of the oneor more second groups; and an indication of whether the second apparatusis a member of each group in the number of groups.
 8. The method ofclaim 7, wherein at least some of the apparatuses in the one or morefirst groups and the one or more second groups are the same.
 9. Themethod of claim 7, wherein the first apparatus and the second apparatusare the same.
 10. The method of claim 7, wherein transmitting the secondmessage comprises transmitting the second message to the secondapparatus during association with the second apparatus.
 11. The methodof claim 1, wherein each of the groups of apparatuses is for receivingsimultaneously transmitted spatial streams.
 12. The method of claim 11,further comprising transmitting the simultaneously transmitted spatialstreams to a group in the one or more first groups, based on theallocated first spatial stream position.
 13. An apparatus for wirelesscommunications, comprising: a processing system configured to:determine, in a number of groups of apparatuses, one or more firstgroups to which a first apparatus belongs; allocate, for the firstapparatus, a first spatial stream position associated with each of theone or more first groups; and generate a first message based on theallocation and the determination; and a transmitter configured totransmit the first message to the first apparatus, wherein the firstmessage comprises: an indication of the allocated first spatial streamposition associated with each of the one or more first groups; and anindication of whether the first apparatus is a member of each group inthe number of groups.
 14. The apparatus of claim 13, wherein thetransmitter is configured to transmit the first message duringassociation with the first apparatus.
 15. The apparatus of claim 13,wherein the first message comprises a field indicating a number of groupidentification (groupID) bits and wherein the number of groups ofapparatuses is based on the number of groupID bits.
 16. The apparatus ofclaim 15, wherein the field indicates that the number of groupID bits isy such that the number of groups of apparatuses is 2^(y).
 17. Theapparatus of claim 13, wherein the indication of whether the firstapparatus is a member of each group comprises one bit for each group inthe number of groups.
 18. The apparatus of claim 13, wherein theindication of the allocated first spatial stream position associatedwith each of the one or more first groups comprises two bits.
 19. Theapparatus of claim 13, wherein the processing system is furtherconfigured to: determine, in the number of groups, one or more secondgroups to which a second apparatus belongs; allocate, for the secondapparatus, a second spatial stream position associated with each of theone or more second groups; and generate a second message based on theallocation and the determination, wherein the transmitter is furtherconfigured to transmit the second message to the second apparatus, andwherein the second message comprises: an indication of the allocatedsecond spatial stream position associated with each of the one or moresecond groups; and an indication of whether the second apparatus is amember of each group in the number of groups.
 20. The apparatus of claim19, wherein at least some of the apparatuses in the one or more firstgroups and the one or more second groups are the same.
 21. The apparatusof claim 19, wherein the first apparatus and the second apparatus arethe same.
 22. The apparatus of claim 19, wherein the transmitter isconfigured to transmit the second message to the second apparatus duringassociation with the second apparatus.
 23. The apparatus of claim 13,wherein each of the groups of apparatuses is for receivingsimultaneously transmitted spatial streams.
 24. The apparatus of claim23, wherein the transmitter is further configured to transmit thesimultaneously transmitted spatial streams to a group in the one or moregroups, based on the allocated first spatial stream position.
 25. Anapparatus for wireless communications, comprising: means fordetermining, in a number of groups of apparatuses, one or more firstgroups to which a first apparatus belongs; means for allocating, for thefirst apparatus, a first spatial stream position associated with each ofthe one or more first groups; means for generating a first message basedon the allocation and the determination; and means for transmitting thefirst message to the first apparatus, wherein the first messagecomprises: an indication of the allocated first spatial stream positionassociated with each of the one or more first groups; and an indicationof whether the first apparatus is a member of each group in the numberof groups.
 26. The apparatus of claim 25, wherein the means fortransmitting the first message is configured to transmit the firstmessage during association with the first apparatus.
 27. The apparatusof claim 25, wherein the first message comprises a field indicating anumber of group identification (groupID) bits and wherein the number ofgroups of apparatuses is based on the number of groupID bits.
 28. Theapparatus of claim 27, wherein the field indicates that the number ofgroupID bits is y such that the number of groups of apparatuses is2^(y).
 29. The apparatus of claim 25, wherein the indication of whetherthe first apparatus is a member of each group comprises one bit for eachgroup in the number of groups.
 30. The apparatus of claim 25, whereinthe indication of the allocated first spatial stream position associatedwith each of the one or more first groups comprises two bits.
 31. Theapparatus of claim 25, further comprising: means for determining, in thenumber of groups, one or more second groups to which a second apparatusbelongs; means for allocating, for the second apparatus, a secondspatial stream position associated with each of the one or more secondgroups; means for generating a second message based on the allocationand the determination; and means for transmitting the second message tothe second apparatus, wherein the second message comprises: anindication of the allocated second spatial stream position associatedwith each of the one or more second groups; and an indication of whetherthe second apparatus is a member of each group in the number of groups.32. The apparatus of claim 31, wherein at least some of the apparatusesin the one or more first groups and the one or more second groups arethe same.
 33. The apparatus of claim 31, wherein the first apparatus andthe second apparatus are the same.
 34. The apparatus of claim 31,wherein the means for transmitting the second message is configured totransmit the second message to the second apparatus during associationwith the second apparatus.
 35. The apparatus of claim 25, wherein eachof the groups of apparatuses is for receiving simultaneously transmittedspatial streams.
 36. The apparatus of claim 35, further comprising meansfor transmitting the simultaneously transmitted spatial streams to agroup in the one or more first groups, based on the allocated firstspatial stream position.
 37. A computer-program product for wirelesscommunications, comprising a computer-readable medium comprisinginstructions executable to: determine, in a number of groups ofapparatuses, one or more first groups to which a first apparatusbelongs; allocate, for the first apparatus, a first spatial streamposition associated with each of the one or more first groups; generatea first message based on the allocation and the determination; andtransmit the first message to the first apparatus, wherein the firstmessage comprises: an indication of the allocated first spatial streamposition associated with each of the one or more first groups; and anindication of whether the first apparatus is a member of each group inthe number of groups.
 38. An access point, comprising: at least oneantenna; a processing system configured to: determine, in a number ofgroups of apparatuses, one or more first groups to which a firstapparatus belongs; allocate, for the first apparatus, a first spatialstream position associated with each of the one or more first groups;and generate a first message based on the allocation and thedetermination; and a transmitter configured to transmit, via the atleast one antenna, the first message to the first apparatus, wherein thefirst message comprises: an indication of the allocated first spatialstream position associated with each of the one or more first groups;and an indication of whether the first apparatus is a member of eachgroup in the number of groups.
 39. A method for wireless communications,comprising: receiving a message comprising, for each group in a numberof groups of apparatuses: an indication of a membership status; and anindication of a spatial stream position; receiving simultaneouslytransmitted spatial streams for one of the groups of the apparatuses,wherein the message and the simultaneously transmitted spatial streamsare received at one of the apparatuses; determining that the one of theapparatuses is a member of the one of the groups based on the indicationof the membership status; and using the indication of the spatial streamposition for the one of the groups to parse the received simultaneouslytransmitted spatial streams.
 40. The method of claim 39, wherein thereceiving the message comprises receiving the message during associationof the one of the apparatuses.
 41. The method of claim 39, wherein themessage comprises a field indicating a number of group identification(groupID) bits and wherein the number of groups of apparatuses is basedon the number of groupID bits.
 42. The method of claim 41, wherein thefield indicates that the number of groupID bits is y such that thenumber of groups of apparatuses is 2^(y).
 43. The method of claim 41,further comprising determining a number of groupID fields in the messageto read based on the number of groupID bits.
 44. The method of claim 39,wherein the indication of the membership status for each group comprisesone bit for indicating whether the one of the apparatuses is a member ofthe group.
 45. The method of claim 39, wherein the indication of thespatial stream position for each group comprises two bits.
 46. Anapparatus for wireless communications, comprising: a receiver configuredto: receive a message comprising, for each group in a number of groupsof apparatuses: an indication of a membership status; and an indicationof a spatial stream position; and receive simultaneously transmittedspatial streams for one of the groups of the apparatuses, wherein theapparatus is one of the apparatuses; and a processing system configuredto: determine that the apparatus is a member of the one of the groupsbased on the indication of the membership status; and use the indicationof the spatial stream position for the one of the groups to parse thereceived simultaneously transmitted spatial streams.
 47. The apparatusof claim 46, wherein the receiver is configured to receive the messageduring association of the apparatus.
 48. The apparatus of claim 46,wherein the message comprises a field indicating a number of groupidentification (groupID) bits and wherein the number of groups ofapparatuses is based on the number of groupID bits.
 49. The apparatus ofclaim 48, wherein the field indicates that the number of groupID bits isy such that the number of groups of apparatuses is 2^(y).
 50. Theapparatus of claim 48, wherein the processing system is furtherconfigured to determine a number of groupID fields in the message toread based on the number of groupID bits.
 51. The apparatus of claim 46,wherein the indication of the membership status for each group comprisesone bit for indicating whether the apparatus is a member of the group.52. The apparatus of claim 46, wherein the indication of the spatialstream position for each group comprises two bits.
 53. An apparatus forwireless communications, comprising: means for receiving a messagecomprising, for each group in a number of groups of apparatuses: anindication of a membership status; and an indication of a spatial streamposition and for receiving simultaneously transmitted spatial streamsfor one of the groups of the apparatuses, wherein the apparatus is oneof the apparatuses; means for determining that the apparatus is a memberof the one of the groups based on the indication of the membershipstatus; and means for using the indication of the spatial streamposition for the one of the groups to parse the received simultaneouslytransmitted spatial streams.
 54. The apparatus of claim 53, wherein themeans for receiving the message is configured to receive the messageduring association of the apparatus.
 55. The apparatus of claim 53,wherein the message comprises a field indicating a number of groupidentification (groupID) bits and wherein the number of groups ofapparatuses is based on the number of groupID bits.
 56. The apparatus ofclaim 55, wherein the field indicates that the number of groupID bits isy such that the number of groups of apparatuses is 2^(y).
 57. Theapparatus of claim 55, further comprising means for determining a numberof groupID fields in the message to read based on the number of groupIDbits.
 58. The apparatus of claim 53, wherein the indication of themembership status for each group comprises one bit for indicating theapparatus is a member of the group.
 59. The apparatus of claim 53,wherein the indication of the spatial stream position for each groupcomprises two bits.
 60. A computer-program product for wirelesscommunications, comprising a computer-readable medium comprisinginstructions executable to: receive a message comprising, for each groupin a number of groups of apparatuses: an indication of a membershipstatus; and an indication of a spatial stream position; receivesimultaneously transmitted spatial streams for one of the groups of theapparatuses, wherein the message and the simultaneously transmittedspatial streams are received at one of the apparatuses; determine thatthe one of the apparatuses is a member of the one of the groups based onthe indication of the membership status; and use the indication of thespatial stream position for the one of the groups to parse the receivedsimultaneously transmitted spatial streams.
 61. A station, comprising:at least one antenna; a receiver configured to: receive, via the atleast one antenna, a message comprising, for each group in a number ofgroups of apparatuses: an indication of a membership status; and anindication of a spatial stream position; and receive, via the at leastone antenna, simultaneously transmitted spatial streams for one of thegroups of the apparatuses, wherein the station is one of theapparatuses; and a processing system configured to: determine that thestation is a member of the one of the groups based on the indication ofthe membership status; and use the indication of the spatial streamposition for the one of the groups to parse the received simultaneouslytransmitted spatial streams.